Project 1 is designed to increase basic knowledge of the etiology and maintenance of severe, chronic aberrant behaviors (CAB) and to develop treatments based on this knowledge. This research program translates basic-research findings from laboratory studies of both animal and human subjects, first to more naturalistic settings and activities, and then to clinical-treatment settings. The laboratory studies have shown, paradoxically, that schedules of positive reinforcement can, in some circumstances, be aversive. When relatively rich conditions of positive reinforcement transition to relatively lean conditions of positive reinforcement, subjects show prolonged, counterproductive disruptions in behavior (pausing). Further, if a means of escape from the situation is provided, subjects escape. That is, negative incentive shifts are aversive, and thus motivate maladaptive escape behaviors. It is important to note that the relatively lean reinforcement conditions are not inherently aversive. It is the context that creates the aversiveness. In the laboratory, these findings have a great deal of generality. In the natural environment, schedules of positive reinforcement are ubiquitous. The present research program is the first to integrate these laboratory findings with the problem of chronic aberrant behavior. In the clinic, a current, successful treatment strategy has been to identify the behavioral function of aberrant behavior on an individual basis (i.e., a functional analysis), and use this information to design treatment. Escape (negative reinforcement) has been shown to be a primary motive for the aberrant behavior of a substantial portion of treated individuals. Explaining, at a behavioral-process level, what makes certain activities aversive for some individuals has not been a primary goal of the treatment-oriented studies. Not surprisingly, given its paradoxical nature, the notion that escape can be a side effect of positive reinforcement has not been applied to either basic or clinical research in this area. Note that we do not suggest that negative incentive shifts account for all of aberrant behavior, or even all of escape-motivated aberrant behavior. Our preliminary work suggests, however, such pausing and escape can provide a functional analogue to a clinically significant portion of aberrant behavior, in that conditions that generate long pausing may predict aberrant behavior. The proposed research will test the utility of this conceptualization in predicting the occurrence of stereotyped and self-injurious behaviors in persons with IDD. In keeping with the translational nature of the research program, studies will be conducted in naturalistic and clinical settings. In the naturalistic setting, three studies are proposed for each of two CAB topographies (self injury/aggression and stereotypy). These studies will generally replicate laboratory procedures, but with modifications to better reflect the conditions of reinforcement and behaviors found in natural environments. In addition, aberrant behaviors, vocalizations, and other behaviors indicative of emotional responses will be observed. Two experiments are proposed in clinical settings. The first is to predict conditions of incentive shift that produce CAB based on relative preference for daily activities. The second clinical study identifies functional reinforcers for CAB, and assesses rich and lean transitions and CAB based on natural, fluctuations in the quantity and quality of these reinforcers in daily clinical activities. This research strategy is geared towards better understanding of the behavioral processes that may provide the motivational conditions for CAB, and to begin the use of this knowledge for developing treatment strategies.